Amprobe PM51A - Manual (Page 6)

4
V dc and V ac Functions
Rotate the rotary selector to the V position. V ac is the default function. The ac annunciator 
appears on the display. Press the SELECT button momentarily to select V dc. The dc annunciator
 appears on the display.
Resistance, Continuity, Diode, and Capacitance Functions
! Turn the rotary switch to the #/(/,/ position. Resistance is the default function.
1. Turn off power to the circuit being measured. Never measure resistance across a voltage source
or on a powered circuit.
2. Discharge any capacitors that may influence the reading.
3. Connect the test probes across the resistance.
4. Read the display. If OL appears on the highest range, the resistance is too large to be measured
or the circuit is an open circuit.
! A continuous beep tone indicates a complete circuit.
1. Turn off power to the circuit being measured.
2. Discharge any capacitors that may influence the reading.
3. Connect the test probes across the resistance or two measurement nodes.
4. Listen for the tone that indicates continuity (< 120 #).
! Press the SELECT button momentarily AGAIN to select Diode test function. The annunciator ,
appears on the display. The reading shows the approximate voltage drop across the test leads.
Normal forward voltage drop (forward biased) for a good silicon diode is between 0.400 V to
0.900 V. A reading higher than that indicates a leaky diode (defective). A zero reading indicates a
shorted diode (defective). OL indicates an open diode (defective). Reverse the test leads
connections (reverse biased) across the diode. The digital display shows OL if the diode is good.
Any other readings indicate the diode is defective.
! Press the SELECT button momentarily AGAIN to select the Capacitance function.
1. Turn off power to the circuit being measured.
2. Discharge the capacitor using a 100 kW resistor.
3. Free at least one end of the capacitor from the circuit.
4. Connect the test probes across the capacitor.
5. Read the display.